1. Field of the Invention
The invention relates to a rotating retractor and pretensioner for a safety belt, especially in motor vehicles. The invention includes a belt retractor, the belt shaft of which supports the belt winding and rotates in the take-up direction of the safety belt when the tensioning drive coupled to the belt shaft is released. The belt shaft is associated with a drivewheel with recesses on the periphery thereof for accepting mass bodies acting as drive means, and the mass bodies are stored in a tube, which tangentially flows into the drivewheel, and the mass bodies are accelerated in the tube by means of a gas generator arranged at one end of the tube.
2. Description of Related Art
A rotating retractor and pretensioner having the above features is described in U.S. Pat. No. 5,881,962. A belt spool of the associated rotating retractor is mounted between the sides of a U-shaped housing, a drivewheel is arranged on an end of the belt shaft protruding over the associated housing arms, the periphery of the drivewheel is provided with dome-shaped recesses for accepting mass spheres as drive means for the drivewheel. In the plane of the drivewheel, a tube, which forms a channel and which preferably has a pyrotechnical drive unit on its end, is fastened to the housing arm, a number of mass spheres being stored in the tube. The channel surrounds the drivewheel in a spiral shape directed from outside to inside in such a manner that the channel flows tangentially into the drivewheel. The channel surrounds the drivewheel and its dome-shaped recesses over part of the drivewheel's periphery and flows into a planar displaced outlet through which the mass spheres conducted into the channel via the drivewheel leave the channel, the belt retractor being provided with an appropriately arranged receptacle for this purpose.
The known rotating pretensioner has the disadvantage that the arrangement of the tube with the channel for accepting mass spheres causes a corresponding space requirement on one side of the belt roller housing, particularly since the arrangement of tube surrounding the drivewheel clearly exceeds the dimensions of the belt roller housing. It is therefore not possible to mount the belt retractor and pretensioner combination in every position in a motor vehicle. Since the receptacle has to be arranged planar-displaced because the tube surrounding the drivewheel within one plane, the belt retractor and pretensioner combination likewise has a correspondingly large overall axial width. Moreover, the one-sided arrangement of the tube also causes a non-uniform weight distribution, potentially causing assembly problems. The continuous bending of the tube to the spiral shape of the channel is expensive to produce and difficult to mount on the belt roller housing.
The object of the invention is therefore to simplify the production and assembly of a tube accepting the mass bodies in a rotating pretensioner having generic features and to permit a more compact construction of the belt retractor and pretensioner combination.
The solution to this problem, including advantageous embodiments and further developments of the invention, follows for the content of the claims, which follow this description.